Title：Multi-wavelength discovery of Quasi-periodic Oscillations in Supermassive black Holes.

Speaker：Ashutosh Tripath ( Xinjiang Astronomical Observatory)

Time: Jan.09th, Thursday, 10:00am

Location: The Middle conference room at the 3rd floor

Abstract：

Quasi-periodic Oscillations (QPOs) have been observed in supermassive black holes (SMBH) across the electromagnetic spectrum. The claimed timescales range from a few tens of minutes to days, weeks, and even a decade. Different models have been proposed to explain these QPOs which are primarily based on the timescales of periodicity. In this talk, I will present the QPOs detected in the X-ray, gamma, and radio light curves of blazars, which constitute the special class of SMBH, and the models employed to explain them. I will show the recent results obtained using the optical data from Transiting Exoplanet Survey Satellite (TESS) which opens the new and exciting field of studying days' timescale variability in these objects. I will also present the recent result where we found interesting radio variability. I will discuss the practical problems encountered in analyzing these light curves (irregularity, gaps, stationarity, etc.) and ways to resolve them using advanced time series analysis methods .

CV：Dr. Ashutosh Tripathi is currently an Associate Professor at Xinjiang Astronomical Observatory, Chinese Academy of Sciences. He obtained his Ph.D. in 2019 at Fudan University, Shanghai in Theoretical Astrophysics. After his first postdoc at Fudan, he moved to Southern Methodist University, Dallas, Texas in 2022 to work on time-domain astronomy with a NASA grant. After a year, in 2023, he moved to Texas A&M University to work as a postdoctoral research associate before joining XAO as a faculty member. His research interests are time-domain multi-messenger astronomy, X-ray reflection spectroscopy, morphologies of galaxies, and machine-learning applications in astrophysics.